Screw rolling die



July 27, 1965 L. GORDON SCREW ROLLING DIE 2 Sheets-Sheet 1 Filed June 11, 1962 L W I m Qw I INVENTOR. lkzoaj' 627w July 27, 1965 L. GORDON 3,196,654

SCREW ROLLING DIE Filed June 11, 1962 2 Sheets-Sheet 2 BY QZSM, f/ z/a United States Patent 3,196,654 SCREW ROLLING DIE Lewis Gordon, Eagle Heights, Elgin, Ill., assiguor to Illinois Tool Works Inc., Chicago, 11]., a corporation of Delaware Filed June 11, 1962, Ser. No. 201,375 4 Claims. (CL 72-88) The present invention relates to a novel method and apparatus for producing threaded workpieces such as screws, and more specifically, to a novel method and apparatus for forming screws havinga generally pointed or tapering entering end.

One practice which has heretofore been followed when producing threaded fasteners or screws of the general type contemplated herein has included the step of swaging and pinching an entering end of a screw blank to provide the blank with a generally pointed tip portion prior to a thread rolling operation. While screws have long been successfully produced in this manner, many attempts have been made to devise a method and apparatus for forming screws with tapered or pointed ends without first subjecting the screw blanks to the pinch pointing operation, whereby to minimize costs by eliminating the time and machinery necessary to accomplish the pinch pointing operation. However, such prior proposals which have utilized rolling dies for forming the pointed tip portion as well as thread convolutions on screw shanks have not been entirely satisfactory, particularly as a result of failure to obtain .a uniform solid point without burrs or long needlelike tails which may result when the material of the blank is extruded from between the rolling dies.

An important object of the present invention is to provide a novel apparatus for producing screws and the like more economically and in a manner which provides the screws with substantially uniform entering end portions or tip structures having the desired characteristics.

A more specific object of the present invention is to .provide a novel apparatus for producing screw elements uniform, solid, tail free tip portions.

Other objects and advantages of the present invention will become apparent from the following description wherein:

FIG. 1 is a perspective view showing a thread rolling die incorporating features of the present invention;

FIG. 2 is an elevational view of the die shown in FIG. 1;

FIG. 3 is a bottom view showing a set of thread rolling dies incorporating features of the present invention;

FIG. 4 is a sectional view taken generally along line 4-4 in FIG. 3;

FIG. 5 shows a screw blank in various stages of development as it passes between the rolling dies;

FIG. 6 is an enlarged fragmentary sectional view taken generally along line 6-6 in FIG. 2; and

FIG. 7 is an enlarged fragmentary sectional view taken generally along line 77 in FIG. 3.

Referring now more specifically to the drawings wherein like parts are designated by the same numerals throughout the various figures, the present invention contemplates the provision of a pair of die members 10 and 12. As will be understood, these die members are adapted to be mounted in a thread rolling machine of known construction for relative reciprocal movement for forming a screw V 3,196,654 Patented July 27, 1965 blank inserted therebetween. The die members 10 and 12 are identical to each other but oppositely arranged in opposing relationship as shown in FIGS. 3 and 4. Therefore in order to simplify the present disclosure only the die member 10 will be described in detail and the reference numerals applied to various elements of the die member 10 will also be applied to identical elements of the die member 12.

The die member 10 comprises an elongated generally rectangular body formed from a suitable tool steel. The body is provided with a plurality of thread forming ribs 14, which ribs extend angularly or somewhat diagonally from a first longitudinal margin 16 toward a second longitudinal margin 18 of a screw or workpiece forming face portion 20 of the die. As shown in FIG. 2 this face portion is defined by corners 22, 24, 26 and 28.

As shown best in FIGS. 2 and 3, a portion of the ribs is removed adjacent the workpiece entering end of the die 10 so as to provide an inclined surface 30 adapted to engage and progressively form a tapering or pointed tip portion on a screw blank prior to the formation of a thread convolution on the tip portion. Furthermore the ribs 20 are constructed for progressively increasing in height from the entering end of the die defined by the corners 22 and 26 toward a mid portion of the die indicated bythe point 32 in FIG. 3 for progressively forming thread convolutions of increased depth in a screw blank. The ribs 14 and grooves 34 therebetween are constructed for providing the workpiece forming face 20 with a substantially uniform profile between the point 32 and the discharge end of the die defined by the corners 24 and 28. This profile is shown in FIG. 4 and in greater detail in FIG. 7.

FIG. 6 shows the profile of the ribs 14 and grooves 34 along a section taken longitudinally of the ribs and grooves as indicated by the section lines 6-6 in FIG. 2. First portions 36 and 38 of the ribs and grooves have parallel edges and bottoms which are in turn substantially parallel to thesurface defined by the margin 18 and the direction of movement of the dies. As the portions 36 and 38 of the ribs and grooves approach the margin 18, they merge with second rib and groove portions 40 and 42 respectively which are inclined outwardly at relatively small angles from the portions 36 and 38, which angles may, for example, be on the order of about 3.5 It will be noted that the crests and bottoms of the rib and groove portions 40 and 42 are still parallel to each other and have the same height or depth asthe crests and bottoms of the rib portions 36 and 38, whereby the rib portions 40 and 42 are adapted to form full depth threads in a screw blank.

As shown in FIGS. 6 and 7, the portion 40 of the ribs extends substantially to the margin 18 and merges with a rounded surface 44 which in turn intersects the margin 18. The surface 44 is rounded in a manner such that its projection taken in a plane perpendicular to the longitudinal axis of the die is substantially in the form of a segment of a circle as shown in FIG. 7 for forming the tip of the screw blank in the manner described in detail below.

The portion 42 of the grooves merges with another groove portion 46 having a bottom inclined at an increased angle with respect to the bottom of the groove portion 38, which angle may for example, be about 8". Thus the groove portion 46 progressively decreases in depth until the bottom thereof intersects the surface of the rib portion 40 at 48. The point of intersection 48 is located substantially away from the margin 18 and the curved surface 44 whereby the portions 40 of the ribs combine together to provide an uninterrupted surface portion 50 between the point 48 and the curved surface 44.

Referring particularly to FIG. 7, it is seen that the angular arrangement of the crest surfaces of the rib portions 40 is such that these rib portions are adapted to form a screw blank with a tapering or generally conical entering end portion during a screw rolling operation. At the same time the groove portions 42 combined with the ribs to form full depth thread segments along a first part of the tapering tip of the screw while the groove portions 46 form thread segments of progressively decreasing height and in a manner such that the thread terminates at a location corresponding to the point 48 and spaced from the extremity of the tip portion. During the formation of the tip portion of the screw, the inclined rib and groove portions cause material of the screw blank to be extruded axially toward the extremity of the screw. At the same time the rounded surface 44 of the blank'forms the material of the blank into a solid tip having a definite terminal point as discussed more fully below.

In accordance with the present invention, a screw blank 52 is utilized, which blank is initially formed so that it has a straight cylindrical shank 54 as shown in FIG. 2 and at the first or left hand position in FIG. 5. It is important to note that the shank 54. of the blank has a length at least substantially as great as and preferably slightly greater than the width of the die face 20 or, in other words, the distance between the margins 16 and 18. In order to initiate a thread rolling operation, the blank 52 is inserted between the entering ends of the die members in the usual manner. Then upon relative longitudinal movement of the die members, the blank successively passes stations 56, 58, 60, 62 and 64 along the die member 10. As the blank moves toward the station 56, helical thread convolutions 66 are partially formed along the shank 54 and a tip portion 68 of the shank is rolled and slightly reduced and tapered. Since,

however, the surface portion 30' of the die is formed 'withoutribs or'grooves as 'Was described above, the portion 68 of the shank initially is not provided with helical thread convolutions. It is to be noted that an extreme tip portion 70 of the screw blank shank 54 projects beyond the margin 18 so that this tip portion avoids engagement with the die face 20 and thus maintains its original diameter.

Further movement of the screw blank along the die and past the stations 58 and'60 causes a more complete formation of the thread convolutions 66 as shown in the third and fourth stations of FIG. 5. At the same time the entering end portions 63 of the screw is progressively formed with the tapered'or conical configuration shown and is formed with additional thread convolutions 70 extending partially thereon. It is important to note that while the entering end portion 68 is being formed, material of the blank is extruded axially outwardly so that the extreme tip portion 70 is shifted laterally outwardly and initially remains joined tothe en'teringend portion 68 by a narrow neck element '74 extending between the opposing margins 18 of the die members 10 and 12.

In accordance with a feature of the present invention, each die member is sharply relieved along its margin 18 for accommodating the relatively large extruded tip portions '70 of the blank. More specifically, the die body is formed with a. generally flat surface 76 which may conveniently be substantially parallel .to the face and offset from the margin 18 by a substantially vertical wall '78. It is further important to note that the wall 78 is formed in a manner such that it fiares from a point adjacent the station 62 laterally away from the margin 18 and toward the discharge end of the die body for providing a laterally projecting abutment or cut-off surface 30.7 With this structure, the extruded tip portion 70 of a screw blank will be engaged by the abutment surface 80 as the blank passes the station 62 whereby the tip portion 70 will be separated from the remainder of the blank by breaking of the neck element '74. Continued movement of the screw blank from the station 62 and -=pastrthe3station d i comprises afinishing step which provides the screw shank, the thread convolutions and the tip portion 68 with the desired uniform finish.

Referring particularly to FIGS. 4 and 7 and the third, fourth and fifth stations in FIG. 5, it is important to note that the surface portions 44- of the die members are curved or, in certain instances, otherwise formed for initially extending from junctions with the margins 18 substantially at right angles with respect to the plane of relative movement of the dies whereby to form the screw tip portion '68 with a rounded or relatively blunt extremity 82. This extremity is, of course, initially integrally joined to the neck element 74. Since the outer extremity of the tip portion 7%) is located laterally of the margins 13 during the rolling operation, the tip portion 76 has its greatest diameter at its outer end and gradually decreases in diameter or cross section along the neck element 74 and to the junction 84- with the tip 82 of the screw. As previously indicated, the tip 32 is provided with a relatively blunt configuration whereby to provide an extremely sharp change in the cross section of the blank at the junction 8 This sharp change in combination with the fact that the junction 34 is smaller in diameter than any other portion of the screw blank causes the tip portion to break away from the remainder of the screw substantially precisely at the junction 84 when the tip portion is engaged by the abutment surfaces 80.

Thus assurance is provided that successive screws formed in accordance with this invention will have substantially uniform tip structures of solid material.

While the preferred embodiment of the present invention has been shown and described herein, it is obvious that many details may be changed without departing from the spirit and scope of the appended claims.

The invention is claimed as follows:

'1. A thread rolling die comprising a workpiece engageable face including generally diagonally disposed ribs for forming helical thread convolutions on a workpiece, said ribs extending from adjacent a first longitudinal margin of said face toward a second longitudinal margin of said face, said die being relieved along' and laterally outwardly of said second margin from an entering end of the dietoward a discharge end of the die for providing a recess and accommodating material of a workpiece projecting laterally of said second margin during a thread rolling operation, and said die including means disposed laterally of said second margin in a direction away from said first margin and traversing said recess for positively engaging said projecting material of the workpiece and breaking said material from the remainder of the workpiece during a thread rolling operation.

2. A thread rolling die comprising a workpiece engageable face including generally diagonally disposed rib and groove means for forming helical'thread convolutions on a workpiece, said rib and groove means extending from adjacent a first longitudinal margin of said face toward and terminating short of a second longitudinal margin of said face, said second margin having a height which increases from adjacent a workpiece entering end of the die and exceeds the height of the rib means adjacent a workpiece discharge end of the die, said second margin having an arcuate concave cross section adjacent said discharge end for forming a rounded portion on said workpiece, said die being relieved along and laterally outwardly of said second margin from adjacent; said entering end toward said discharge end for accommodating material of the workpiece projecting laterally of said second margin and said rounded portion during a thread rolling operation, and said die including means disposed laterally of said second margin in a direction away from said first mentioned margin and located adjacent said discharge end and having a height substantially no greater than the height of said second margin adjacent the discharge end for positively engaging said projecting material of the workpiece and breaking said material from the remainder of the workpiece during athread rolling operation.

3. A thread roiling die comprising a workpiece engageable face including generally diagonally disposed rib and groove means for forming heiical thread convolutions on a workpiece, said rib and groove means extending from adjacent a first longitudinal margin of said face toward and terminating short of a second longitudinal margin of said face, said face including a surface portion between said rib and groove means and said second margin for forming a relatively blunt tip on a workpiece during a thread roiling operation, said surface portion having an arcuate concave cross section adjacent said dis- Charge end, said die having a recess along said second margin from adjacent an entering end of the die toward a discharge end of the die for accommodating any material of the workpiece projecting laterally of said second margin during a thread rolling operation, and said die including means disposed adjacent and laterally of said second margin and spaced from said entering end of the die and obstructing said recess for positively engaging said projecting material of the workpiece projecting lat- References Cited by the Examiner UNITED STATES PATENTS 1,232,876 7/ 17 Wilcox 80-'-9 1,913,143 6/33 Robertson 8061 3,019,677 2/62 Cermatori 809 FOREIGN PATENTS 244,493 3 12 Germany.

WILLIAM J. STEPHENSON, Primary Examiner.

CHARLES W. LANHAM, Examiner. 

1. A THREAD ROLLING DIE COMPRISING A WORKPIECE ENGAGEABLE FACE INCLUDING GENERALLY DIAGONALLY DISPOSED RIBS FOR FORMING HELICAL THREAD CONVOLUTIONS ON A WORKPIECE, SAID RIBS EXTENDING FROM ADJACENT A FIRST LONGITUDINAL MARGIN OF SAID FACE TOWARD A SECOND LONGITUDINAL MARGIN OF SAID FACE, SAID DIE BEING RELIEVED ALONG AND LATERALLY OUTWARDLY OF SAID SECOND MARGIN FROM AN ENTERING END OF THE DIE TOWARD A DISCHARGE END OF THE DIE FOR PROVIDING A RECESS AND ACCOMMODATING MATERIAL OF A WORKPIECE PROJECTING LATERALLY OF SAID SECOND MARGIN DURING A THREAD ROLLING OPERATION, AND SAID DIE INCLUDING MEANS DISPOSED LATERALLY OF SAID SECOND MARGIN IN A DIRECTION AWAY FROM SAID FIRST MARGIN AND TRAVERSING SAID RECESS FOR POSITIVELY ENGAGING SAID PROJECTING MATERIAL OF THE WORKPIECE AND BREAKING SAID MATERIAL FROM THE REMAINDER OR THE WORKPIECE DURING A THREAD ROLLING OPERATION. 